Re: [PATCH v4 0/5] road to reentrant real_path

[Brandon Williams <bmwill@google.com>]

On 01/04, Jacob Keller wrote:
> On Wed, Jan 4, 2017 at 10:22 AM, Stefan Beller <sbeller@google.com> wrote:
> > On Wed, Jan 4, 2017 at 10:13 AM, Brandon Williams <bmwill@google.com> wrote:
> >> On 01/04, Jeff King wrote:
> >>> On Wed, Jan 04, 2017 at 07:56:02AM +0100, Torsten Bögershausen wrote:
> >>>
> >>> > On 04.01.17 01:48, Jeff King wrote:
> >>> > > On Tue, Jan 03, 2017 at 11:09:18AM -0800, Brandon Williams wrote:
> >>> > >
> >>> > >> Only change with v4 is in [1/5] renaming the #define MAXSYMLINKS back to
> >>> > >> MAXDEPTH due to a naming conflict brought up by Lars Schneider.
> >>> > >
> >>> > > Hmm. Isn't MAXSYMLINKS basically what you want here, though? It what's
> >>> > > what all other similar functions will be using.
> >>> > >
> >>> > > The only problem was that we were redefining the macro. So maybe:
> >>> > >
> >>> > >   #ifndef MAXSYMLINKS
> >>> > >   #define MAXSYMLINKS 5
> >>> > >   #endif
> >>> > >
> >>> > > would be a good solution?
> >>> > Why 5  ? (looking at the  20..30 below)
> >>> > And why 5 on one system and e.g. on my Mac OS
> >>> > #define MAXSYMLINKS     32
> >>>
> >>> I mentioned "5" because that is the current value of MAXDEPTH. I do
> >>> think it would be reasonable to bump it to something higher.
> >>>
> >>> > Would the same value value for all Git installations on all platforms make sense?
> >>> > #define GITMAXSYMLINKS 20
> >>>
> >>> I think it's probably more important to match the rest of the OS, so
> >>> that open("foo") and realpath("foo") behave similarly on the same
> >>> system. Though I think even that isn't always possible, as the limit is
> >>> dynamic on some systems.
> >>>
> >>> I think the idea of the 20-30 range is that it's small enough to catch
> >>> an infinite loop quickly, and large enough that nobody will ever hit it
> >>> in practice. :)
> >>
> >> I agree that we should have similar guarantees as the OS provides,
> >> especially if the OS already has MAXSYMLINKS defined.  What then, should
> >> the fall back value be if the OS doesn't have this defined?  5 like we
> >> have done historically, or something around the 20-30 range as Torsten
> >> suggests?
> >
> > As a fallback I'd rather go for a larger number than too small.
> > The reason for the existence is just to break an infinite loop
> > (and report an error? which the current code doesn't quite do,
> > but your series actually does).
> >
> > If the number is too large, then it takes a bit longer to generate the error
> > message, but the error path is no big deal w.r.t. performance, so it's fine
> > for it taking a bit longer.
> >
> > If the number is too low, then we may hinder people from getting actual
> > work done, (i.e. they have to figure out what the problem is and recompile
> > git), so I'd think a larger number is not harmful. So 32?
> >
> 
> I think I agree as well.
> 
> Thanks,
> Jake
> 
> >>
> >> --
> >> Brandon Williams

That's two people for 32.  I'll use that as the fallback and resend the
series.

-- 
Brandon Williams